Hardening photographic gelatin emulsions and gelatin solutions



Patented Dec. 8, 1936 HARDENING PHOTOGBAPHIC GELATIN- EMULSIONS AND GELATIN SOLUTIONS Cyril J. Stand and Richard Briggs, Rochester,

Y., assignors, by mesne assignments, to

Eastman Kodak Company, Jersey City, N. J., a

corporation of New Jersey No Drawing. Application August 4, 1934 Serial No. 738,559

16 Claims. (01. 95-1) This invention relates to photographic. materials and more particularly to the hardening of gelatin, either when applied as an emulsion layer on photographic films, plates, or papers, or when-applied in the form of a solution as a simple coating or sizing for paper or similar materials.

In the preparation of photographic emulsions it has been the practice for many years to overcome the tendency of the gelatin to melt, or to swell during development, particularly at high temperatures, by addition of various so-called hardening agents, the most well-known of which appear to be chrome alum and formaldehyde. Other materials such as acrolein, glyoxal and derivatives of g lyoxal have been proposed for this purpose, but none of these materials has proved to meet all the demands which have been put upon them, especially from 'the photographic standpoint. 1

We have now discovered, however, that the diketones are effective in enablinggelatin emul- 'sions and gelatin layers in general to resist rel a= tively elevated temperatures without undue swelling and, in the case of sensitized materials, to do so with less production of fog or desensitizing than other materials.

It is accordingly an object of the present invention to overcome the difficultie's encountered in the use of known hardening agents and to provide a method whereby gelatin emulsions may be givena satisfactory degree of hardening. Another object is to provide a photographic emulsion which will resist relatively elevated temperatures without melting and which will do so 5' ,without objectionable fogging, or desensitizing.

' Another object is to provide a method of hard- I ening gelatin solutions or layers in general whether in the form of photographic emulsions or merely in the form of a protective coating,

applied to paperanigsim lar surfaces. A furing agents such as chrome alum andformalde hyde. Other objects will appear hereinafter.

We have found that the above objects may be accomplished by incorporating'into the gelatin emulsion or solution one of the' dialkyl, diaryl, or

.alkaryl diketones, for example, diacetyl, acetyl caproyl, acetyl benzoyl, or mixtures thereof.

In'the following examples we have set forth several of the preferred embodiments of ourinvention, but they are included merely for purposes of illustration and not as a limitation The diacetyl may be added as a. 10 per cent solution in methanol or other suitable solvent in which case 2 c. c. of the solution are added. The emulsion is then coated on a plate orother sup port in the usual manner.

As illustrating the beneficial effects of the addition of a diketone to a gelatin in accordance with our invention, an emulsion'produced as above can be satisfactorily processed at 100 F. employing developing bath, wash water, fixing bath and final wash at that temperature, whereas an ordinary gelatin emulsion not containing a hardener in accordance with our invention melts and runs off the plate at 85 F. The hardening appears somewhat progressive with melted and is being held at approximately 40 C.

time and is noticeably greater after, for instance, 7 14 days incubation at 113 F. Even under these conditions, diacetyl, for example, does not give rise to serious fog or desensitizing of the emulsion.

Example II .-To 200 c. c. of a gelatin emulsion 'of the same general type as that described in- Example I there are added 2 c. c. of a 10% methanol solution of acetyl benzoyl the emulsion being melted and held at about 40 C. The emulfound to process satisfactorily without objectionable softening or melting of the emulsion at temperatures as high as 85 F. It ,will be noted that the hardening effect is somewhat less drastic in this case, but this is due solely to the fact that a lower mol. per cent of the hardening agent is employed for the same amount of gelatin.

As is the case with the product obtained in sion is then coated on a suitable support and is Example I, the product'showed an increase in H melting point of only about 15 F. after'incubaflf tion at 113 F. for 14 days.- Example III.To 200 c. c. of a moderatel sensitive photographic emulsion comprising a silver halide there is added 2 grams of acetyl caproyl under the conditions of the previous examples and an'emulsion is thereby produced which processes satisfactorily at 85 F. upon two acetyl, acetyl, caproyl and acetyl benzoyl )the weeks incubationmay be processed at temperatures as high as 100' F. 1

I'he above examples are, as indicated, merely illustrative and many changes may be made in the various manipulative procedures, tempe'ratures, concentrations and ingredients within the scope of our invention depending on the type of gelatin used, and the results desiredin the ilnished product. While we have chosen to illustrate our invention by specific reference to dibroad scope thereof includes the dialkyl. ketones in general; of which diacetyl is possibly the most representative and including acetyl caproyl; the diaryl diketones, of which dibenzoyl is typical; and the alkaryl diketones such as acetyl benzoyl.

Our invention is applicable not only ,to the manufacture of photographic emulsions of satisfactory hardening properties, but may likewise be applied to the manufacture of gelatin solutions which are used forproducing other types of coatings or layers on paper, cloth, film and other surfaces.

We have also found as indicated above that the hardening effect of these 'diketones increases with increasing pH to an optimum value;'which may vary with diflerent gelatines, but in these used was found to be of the order of pH==8, and that they may be used as an adjunct to other hardening-agents, such as various .aliphatic and other aldehydes, including formaldehyde and also chrome alum.

What. we claim is:

i. In the manufacture of photographicarticles provided with a hardened gelatin layer, the step which comprises hardening the gelatin by causing it to react with a diketone, whereby a condensation product of gelatin and the diketone is formed. I

2-. In the manufacture of photographic articles provided with a hardened gelatin layer, the step which comprises hardening the gelatin by causing it to react with a diketone selected from the group comprising the dialkyl diketones, the diaryl diketones, and the alkaryl diketones, whereby a condensation product of gelatin and the diketone is iormed.

3. In the manufacture of photographic articles provided with a hardened gelatin layer, the step which comprises hardening the gelatin by causing it to react with diacetyl, whereby a condensatlon product of gelatin and diacetyl is formed.

4. In the manufacture of photographic articles provided with a hardened gelatin layer, the step which comprises hardening the gelatin by causingit to react with acetyl-caproyl, whereby a condensation product of gelatin and acetyl caproyl 5. In the manufacture of photographic articles provided with a hardened gelatih'layer, the step. which comprises hardening the gelatin by caus- 'cles provided with a hardened gela 8. A photographic material provided with a gelatin silver halide emulsion layer, said layer containing the condensatipnproduct of gelatin and a diketone selected from the group comprising the dialkyl, diketones, the diaryl diketones, and the alkaryl diketones. r

9. A photographic material provided with a .ing it to react with acetyl benzoyl, whereby a gelatin silver halide emulsion layer, said layer containing the condensation product ,of gelatin and diacetyl. v

10. A photographic material provided with a gelatin silver halide emulsion layer, said layer containing the condensation product of gelatin. and acetyl caproyl.

11. A photographic material provided with a gelatin silver halide emulsion layer, said layer containing the condensation product of gelatin and acetyl benzoyl.

12. A composition of matter comprising a solution of gelatin containing diacetyl, said solution being adapted for the production of a hardened gelatin layer containing the condensation product of gelatin and diacetyl. I

13. In the-manufacture of photo aphic artilayer, the

stepwhich comprises hardening thegelatin by causing it toreact with a diketone in which the" carbonyl groups are adjacent, whereby a condensation product of gelatin and the diketone is formed;

14. The process of producing a hardened gelatin emulsion layer which comprises adding a solutibnof a diketone to the melted emulsion'at a temperature of approximately 40 0., whereby a condensation productof gelatinand the diketone is formed, and thereaiter coating theimelted emulsion on a suitable support.

' 15.'A composition of matter comprising a solution of' gelatin containing acetylcap'royl and adapted for the production of a hardened gelatin layer containing the condensation product of gelatin and acetyl 'caproyl. a

16. A composition of matter comprising a solution of gelatin containing acetyl benzoyl and adapted for the production of a hardened gelatin layer containing the condensation product of gelatin and acetyl benaoyl.

' CYRILJ. STAUD.

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